This invention is directed to a robotic device capable of positioning a working implement in a precise and reproducible spatial location with respect to a reference of origin and dynamically repositioning said working implement at a further spatial location which is precisely and reproducibly located with respect to said reference of origin.
Machine tools and other devices exist for the manufacture of components having precise tolerances and precise shapes. Until very recently, these machine tools all required a human operator for their function. Other manufacturing techniques and technology such as welding, riveting or assembly also until very recently were impossible without a human to perform these functions.
With all tasks which require a human operator or a human technician, included in the costs associated with the task is the cost of the human labor. In many instances, the labor costs associated with any one task greatly overshadow all other costs associated with the task. Because of this, in the past, the cost of many manufactured items was directly dependent upon the labor costs.
Aside from economic considerations, human labor has other influences and consequences. Humans are dynamic animals. They have good days and they have bad days. They get ill, they get tired, and they are emotional. All of these factors come into play with respect to the quality and reproducibility of tasks performed by humans. Articles produced by a human operator in the morning when the operator is "fresh" may differ in quality from those produced by the same operator later on in the day, after the drudgery of the day's work has taken its toll on the performance of the human operator.
In order to remove the human operator and/or human technician from certain manufacturing and assembly tasks, certain existing manufacturing machinery has been automated. Examples of such automated machinery are machine tools which are controlled by a taped program with respect to execution of a sequence of operations. Certain of these machine tools have even been equipped with tool carousels to allow for utilization of different tools. While this represents a dramatic step forward toward automation of operation, the existing automated machines still are "dedicated" with respect to the tasks they can perform. A milling machine, whether or not it is automated, is still only capable of performing milling operations. It is static and stationary, requiring the work to be brought to it, and not it to the work.
For certain operations which in the past required a human technician, such as welding or assembly, a class of robotic devices have been developed. For the most part these robotic devices mimic the function of a human arm. They consist of a series of segments which are connected together about axes of rotation to form an articulated arm. Generally, the axes of rotation would be orthogonal in order to give the articulated arm the ability to move within three dimensional space. The arm segments extend from the base and have a working implement on the end of the arm distal from the base. The arm thus forms a cantilever between the base and the working implement.
While articulated arms represent great steps forward with respect to automating certain tasks, they are not without their problems and/or limitations. Because the arm is a cantilever supported at only one end on the base, the loads which the implement can carry or the force which the implement can apply are limited. Additionally, as the implement moves toward or away from the base the lever arm between the implement and the base is variable. This, along with several different axes of rotation within the articulated arm contributes to the difficulty of computer numerical control, "CNC", of these devices.
The variability of the lever arm of a cantilevered articulated arm also contributes to a loss of accuracy with respect to these devices. The accuracy of these devices is best when the lever arm is short. As the lever arm is elongated, the accuracy degrades. In addition, each time a point of rotation must be traversed in moving from one segment of the cantilevered arm to the next, a degradation of the accuracy of the device also occurs. Because the arm is cantilevered, there is a bending moment in each of the individual points of rotation. Since the degradation of the accuracy is cumulative, by the time one reaches the implement end of the arm the accuracy of the arm is severely compromised.
It is thus evident that while current automated machine tools are capable of highly accurate operations, they are expensive, immobile and dedicated devices. Further, while articulated arms can be utilized to perform functions not available with machine tools, they too are extremely expensive, complicated to program and have limited accuracy.